A smart CMOS imager with pixel level PWM signal processing

A PWM signal CMOS imager which realizes block averaging and 2D projection of a thresholded image, in addition to row-parallel PWM readout with high-resolution gray scale, is reported. A pixel including a photo detector executes nondestructive conversion of integrated photo current to PWM signals or binary signals, which drives a readout bus in voltage or current mode. The average and 2D projection are realized with PWM signal addition techniques based on switched current integration and charge packet counting. An experimental imager including 56/spl times/56 pixels, an address signal generator, and a signal processing circuit are fabricated in a 6 mm/spl times/6 mm chip with a 0.8 /spl mu/m CMOS technology. The PWM imager consumes only 2 /spl mu/W/pixel at a 3.3 V supply voltage for a readout operation.

[1]  Eric R. Fossum,et al.  CMOS image sensors: electronic camera-on-a-chip , 1997 .

[2]  B. Wooley,et al.  A 128/spl times/128-pixel standard CMOS image sensor with electronic shutter , 1996, 1996 IEEE International Solid-State Circuits Conference. Digest of TEchnical Papers, ISSCC.

[3]  Abbas El Gamal,et al.  A Nyquist rate pixel level ADC for CMOS image sensors , 1998, Proceedings of the IEEE 1998 Custom Integrated Circuits Conference (Cat. No.98CH36143).

[4]  M. Nagata,et al.  A minimum-distance search circuit using dual-line PWM signal processing and charge-packet counting techniques , 1997, 1997 IEEE International Solids-State Circuits Conference. Digest of Technical Papers.

[5]  Makoto Nagata,et al.  A PWM signal processing core circuit based on a switched current integration technique , 1998, IEEE J. Solid State Circuits.